The present invention relates to a multi-beam optical apparatus for guiding laser beams which are exited from a plurality of light sources onto targets and, in particular, a multi-beam optical apparatus for controlling write timings relative to respective targets by controlling the exiting timing of each laser beam, and an image forming apparatus equipped with the multi-beam optical apparatus.
Generally, as the multi-beam optical apparatus there is known a light exposure device incorporated into an image forming apparatus such as a color copying machine, etc. The light exposure device comprises a plurality of light sources exiting laser beams based on color-separated image signals, a plurality of mirrors and of lenses conducting laser beams which are exited from the respective laser beam sources onto the surfaces (hereinafter referred to simply as drum surfaces) of photosensitive drums prepared for respective colors, and a plurality of polygon mirrors provided correspondingly to the respective laser beam sources and allowing the laser beams which are to be conducted to the respective drum surfaces to be deflected along the directions (horizontal directions) of the rotation shafts of the respective rotation drums to scan the drum surfaces.
In the type of a light exposure device, in order to detect the timings of writing the respective laser beams in the horizontal scanning directions, portions of the laser beams reflected on the respective polygon mirrors are reflected to corresponding reflection mirrors, so that they are received by a corresponding number of light receiving elements. And the timings in which writings are effected by the respective laser beams are controlled based on the laser beams-received by the light receiving elements.
As understood from the above, in the light exposure device of the conventional color copier, it is necessary to, as a structure for detecting the timings of effecting writings by the respective laser beams in the horizontal direction, provide a plurality of reflection mirrors and of light receiving elements so as to correspond to the corresponding mirrors. For this reason, many more components parts are required for the light exposure device and, in addition, the manufacturing cost becomes high.
Further, due to the presence of these many component parts involved, it takes a lot of time to adjust the optical paths of the laser beams conducted to the respective component parts and also much time is required to assembly the light exposure device.